The process of circuit design can cover systems ranging from complex electronic systems to individual transistors within an integrated circuit. Formal circuit design usually includes generating a specification based on customer application, synthesizing a schematic circuit diagram for the specifications, calculating component values to meet the specifications under specified conditions, performing simulations to verify the design, building a prototype and testing against the specification, and other steps that can facilitate manufacturing the circuit appropriately. Circuits can often be designed by one or more circuit designers following a systematic approach with intelligently guided computer simulation. Such computer simulation tools can facilitate efficient and accurate design of circuits, both simple and complex, including analog and digital filters.